1. Field of the Invention
This invention relates to an improved, process for preparing nonphytotoxic micronutrient compositions in horticultural spray oils. As a result of the improvement disclosed herein, blockage of the discharge lines of the reaction vessel by one of the byproducts of the process is eliminated thereby improving the overall economics of the process.
2. Description of the Prior Art
Coassigned U.S. Pat. Nos. 4,003,994 and 4,125,395 describe metathetical processes for preparing a micronutrient compostition containing an overbased oil soluble naphthenate of molybdenum, copper, zinc, manganese and iron by reacting a solution of naphthenic acids having a molecular weight ranging from about 200 to about 620 in a light aromatic solvent of low viscosity having a boiling point ranging up to about 300.degree. F. with alcoholic solutions of alkali hydroxide and of an inorganic salt of the selected metal, water being added and/or the hydrated inorganic salt being used in the case of manganese; the ratio of equivalents of metal to naphthenic acid being from about 1 to about 20; distilling off the solutions including some of the aromatic solvent, mixing with the remainder a horticultural spray oil comprising a nonphytotoxic hydrocarbon mineral oil having a minimum API gravity of 27; a viscosity at 100.degree. F. of between 55 and 100 SUS; and a boiling point range between about 85.degree. and 775.degree. F., removing substantially all the aromatic hydrocarbon solvent in the resulting mixture by vacuum distillation up to a liquid temperature not greater than 130.degree. C., and giving the resulting composition a final polishing by removing any fine particles by centrifugation.
As above described the metathetical route is a highly versatile one for preparing overbased metal salts. It enables basically the same equipment and procedure to be used for preparing a wide variety of overbased metal salts. Usually the metal salt feedstock is the chloride as this is generally soluble in methanol. The system may contain little or no water. Practical problems are encountered when attempts are made to use the cheaper metal sulphate as the source of the metal. The economic advantages of using the sulfate can be appreciated by considering the prices published in the "Oil, Paint and Drug's Chemical Marketing Reporter", July 10, 1978. As shown below, copper, ferrous and manganous sulphates are substantially cheaper than the corresponding chlorides and also provide cheaper sources of the metal.
______________________________________ Price per 100 Item pounds (US,$) ______________________________________ 1.1 CuSo4 . 5H.sub.2 0. (Published Price) 35.45 1.2 CuCl.sub.2 (Published Price) 90.00 1.3 Elemental Cu, Basis CuSO.sub.4 . 5H.sub.2 0 price 103.52 1.4 Elemental Cu, Basis CuCl.sub.2 price 190.57 2.1 FeSO.sub.4 . (Published Price) 2.60 2.2 FeCl.sub.2 (Published Price) 4.70 2.3 Elemental Fe, Basis FeSO.sub.4 price 7.07 2.4 Elemental Fe, Basis FeCl.sub.2 price 10.68 3.1 MnSO.sub.4 (28% Mn, gran.; Published Price) 5.50 3.2 MnCl.sub.2 Published Price 31.00 3.3 Elemental Mn, Basis MnSO.sub.4 price 19.64 3.4 Elemental Mn, Basis MnCl.sub.2 price 71.06 ______________________________________